TDA3618 datasheet(18/24 Pages) PHILIPS

18 / 24 page

1999 Sep 01

Philips Semiconductors

Preliminary speciﬁcation

Multiple voltage regulator with switch and

ignition buffers

TDA3618JR

Application information

NOISE

Table 1

Noise ﬁgures

Note

1. Measured at a bandwidth of 200 kHz.

The noise on the supply line depends on the value of the

supply capacitor and is caused by a current noise (the

output noise of the regulators is translated to a current

noise by the output capacitors). When a high frequency

capacitor of 220 nF in parallel with an electrolytic capacitor

of 100

µF is connected directly to pins 1 and 14 (supply

and ground), the noise is minimal.

STABILITY

The regulators are stabilized with the externally connected

output capacitors.

The output capacitors can be selected by using the graphs

of Figs 9 and 10. When an electrolytic capacitor is used,

the temperature behaviour of this output capacitor can

cause oscillations at a low temperature. The two examples

below show how an output capacitor value is selected.

Example 1

Regulators 1 and 3 are stabilized with an electrolytic

output capacitor of 220

µF (ESR = 0.15 Ω). At −30 °C, the

capacitor value is decreased to 73

µF and the ESR is

increased to 1.1

Ω. The regulator remains stable at

−30 °C.

Example 2

Regulator 2 is stabilized with a 10

µF electrolytic capacitor

(ESR = 3

Ω). At −30 °C, the capacitor value is decreased

to 3

µF and the ESR is increased to 23.1 Ω. Using Fig.10,

the regulator will be instable at

−30 °C.

Solution

To avoid problems with stability at low temperatures, the

use of tantalum capacitors is recommended. Use a

tantalum capacitor of 10

µF or a larger electrolytic

capacitor.

REGULATOR

NOISE FIGURE (

µV)(1)

Co =10 µFCo =47 µFCo = 100 µF

tbf

150

tbf

150

tbf

200

tbf

Fig.9

Curve for selecting the value of output

capacitor for regulators 1 and 3.

handbook, halfpage

0.1

C (

µF)

MGK612

stable region

maximum ESR

100

(

Ω)

Fig.10 Curve for selecting the value of output

capacitor for regulator 2.

handbook, halfpage

0.22

110

C (

µF)

MGK613

stable region

maximum ESR

minimum ESR

100

(

Ω)

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